1. Field of Invention
The present invention relates to the nondestructive inspection of fusion bonded laminated articles.
2. Description of the Prior Art
Many articles of manufacture are constructed by fusion bonding first and second layers of material together by the application of heat and pressure. This type of bonding is particularly suitable in the plastics industry in which the article material readily responds to the fusing process. A type of article particularly suited for the bonding process is one of the inflatible type such as inflated buildings and stabilized balloons as used in communications, weather stations and the like. Such articles are fabricated of layers of cloth and synthetic materials fused together at numerous seams.
The problem with such articles is that it has been extremely difficult to detect a poor or marginal seam until the article actually has been inflated and utilized for its particular purpose. A seam failure at that time may cause destruction of the article and is extremely costly.
In the manufacture of such an article, a solid adhesive is disposed between the first and second layers to be joined together. The seam is placed under heat and pressure which fuses the solid adhesive material causing it to provide a bond between the layers. The usual way for testing such a seam is to inflate the article and, if the article does in fact inflate, then it is assumed that the article is acceptable. However, the application of too little heat or too much heat may result in the seam being weak and the point for subsequent failure. The only practical way in the prior art of detecting the strength of the seam is to test to destruction by overstressing the article. However, the manufacture of one article by a given process does not necessarily guarantee that all articles will conform ideally to the requirements of the process.